Key Milestones Achieved in ProstACT Global Phase 3 Study of TLX591-Tx

Telix Pharmaceuticals has announced that the initial part of its ProstACT Global Phase 3 study has reached its primary objectives by successfully demonstrating the safety and tolerability of its therapeutic candidate, TLX591-Tx (lutetium-177 rosopatamab tetraxetan). This lead-in phase focused on safety and dosimetry, confirming the agent’s acceptable profile without revealing any new safety issues.

Part 1 of the study involved a cohort of 36 patients with prostate-specific membrane antigen (PSMA) positive metastatic castration-resistant prostate cancer (mCRPC). These patients had previously been treated with an androgen receptor pathway inhibitor (ARPI). The investigational therapy was administered in two doses, 14 days apart, alongside one of three standard care treatments—abiraterone, enzalutamide, or docetaxel. The study observed the safety profile, biodistribution, and dosimetry of the treatment, finding them consistent with previous studies of this radio antibody-drug conjugate.

The trial demonstrated that the dosimetry profile was homogeneous across the cohorts, with no significant adverse drug-drug interactions reported. Hematologic events, such as thrombocytopenia and neutropenia, were transient and manageable, aligning with expectations for this therapeutic category. Non-hematologic adverse effects were mostly low-grade, with fatigue, nausea, and dry mouth being the most common.

Insights into Next Research Stages

Following the success of Part 1, Telix has progressed into Part 2 of the study, which involves a broader 2:1 randomized expansion. This phase will continue in various regions, including Australia, New Zealand, and Canada, and has also received regulatory approval in several other countries. The data from Part 1 will be submitted to the United States Food and Drug Administration for consideration of an amendment to proceed with Part 2 in the U.S.

Dr. Neeraj Agarwal, a leading figure in the study, emphasized the feasibility of combining TLX591-Tx with contemporary standard care treatments for mCRPC. Telix’s Group Chief Medical Officer, Dr. David N. Cade, highlighted the ongoing need for improved first- and second-line treatment options for advanced prostate cancer, expressing optimism about the potential of TLX591-Tx as a new therapeutic approach.

Research Context and Future Directions

The ProstACT Global study is a multicenter, international trial aimed at assessing the efficacy of a PSMA-targeted therapeutic in combination with standard care compared to standard care alone. The study design aims to reflect current global clinical practices in treating advanced prostate cancer.

While TLX591-Tx has not yet secured marketing authorization, its distinctive targeting and pharmacological properties have so far shown promising safety results, particularly regarding organ toxicity and common side effects associated with other PSMA-targeted therapies. Further details about the study can be found on Telix’s official website.

Both Illuccix and Gozellix, key tools used for imaging assessments in this trial, have received regulatory approvals, with Illuccix being available in multiple global markets and Gozellix approved by the U.S. FDA.